Here Maps and 3G

I was just wondering something. I live in France and I'm going to Italy for a few days in 3 days, and I downloaded maps for the whole Latium area (Rome) on my phone so that I can use the maps without any 3G connection (I'm going to disable 3G because it is really expensive) but my question is about the locating service. When your phone is locating you, with datas disabled, does it really use only the GPS (if my Nokia Lumia 920 got one) or does it also uses data?